I'm creating a react app that I want my users to embed on their websites. This app will be shown in two iframes but I want to only show one iframe at a time. So one part of the app would be a simple button, the second would be a form that pops up once a user has decided to use the app (it's a chat app.)

I have set up a very simple component that displays the button so that it can send a message to the parent website. I'm not sure what I'm doing wrong but when the window.postmessage event is sent, I get the error:

Uncaught DOMException: Blocked a frame with origin "http://localhost:3002" from accessing a cross-origin frame.

Here is the example parent website code:

<h1>Hello! This is some static content</h1>

    <iframe src="http://localhost:3002"

        style="width: 108px; height: 50px; padding: 0px; margin: 10px 20px; position: fixed; bottom: 0px; right: 0px; overflow: visible; opacity: 1; border: 0px; z-index: 999998; transition-duration: 250ms; transition-timing-function: cubic-bezier(0.645, 0.045, 0.355, 1); transition-property: opacity, top, bottom;"

        id="dbhchat"></iframe>

    <h3>Thanks for checking out my blog!</h3>

    <script>

        window.addEventListener('message', event => {

            // IMPORTANT: check the origin of the data! 

            if (event.origin.startsWith('http://localhost:3002')) {

                // The data was sent from your site.

                // Data sent with postMessage is stored in event.data:

                console.log(event.data);

            } else {

                // The data was NOT sent from your site! 

                // Be careful! Do not use it. This else branch is

                // here just for clarity, you usually shouldn't need it.

                return;

            }

        });

    </script>

and my component that sends the message to the parent window:

import React from 'react';

import { IconButton } from '@material-ui/core';

import PhotoCamera from '@material-ui/icons/PhotoCamera';

import './App.css';



function App() {

  const send = () => {

    if (window && window.parent) {

      console.log('we have message sending here', window.parent);

      window.parent.postMessage('message', 'http://localhost:3002', false);

    }

  }

  return (

    <div className="App">

      <header style={{ background: 'red' }} className="App-header">

        <IconButton onClick={send} color="primary" aria-label="upload picture" component="span">

          <PhotoCamera />

        </IconButton>

      </header>

    </div>

  );

}



export default App;

Thanks in advance for any help figuring this out!